The invention relates to a labeling machine.
As a general rule, a conventional labeling machine comprises a conveyor for transporting articles to be labeled and a labeling head mounted on a bracket extending over the conveyor and fitted with label-gripper means that hold the label in a plane parallel to the face of an article in register with the labeling head. Applicator means secured to the labeling head are adapted to move the label held by the gripper means onto the article that is to be labeled. The labeling head moves on the bracket in a direction perpendicular to the travel direction of the conveyor.
In order to adjust the position of the label on the article, the movement of the labeling machine head on the bracket is controlled as is the advance of the conveyor in such a manner as to cause a reference point on the labeling machine head to coincide with a reference point on the article, in general the corner of a label-receiving zone on the article.
The labeling machine is sometimes required to be capable of positioning the label on the article in any specified orientation. In order to be able to do this, the labeling head of such a labeling machine can turn about a pivot axis.
However, if no special precautions are taken, then turning of the labeling head gives rise not only to a change in the orientation of the label relative to the article, but also to an offset in the position of the label relative to the position expected for it on the article. This offset is either the result of the reference point of the labeling head not coinciding with the pivot axis of the labeling head, or else the result of the label being offset relative to the pivot axis.
In order to remedy that offset, it is appropriate to correct the position of the article relative to the labeling head in the travel direction of the conveyor by moving the conveyor forwards or backwards, and in a direction that is perpendicular thereto by moving the labeling head on the bracket so as to reposition the pivoted label relative to the article. These correcting displacements make it awkward to position a label relative to an article. Furthermore, these displacements vary with varying angle of rotation for the labeling head, further complicating control of pivoting of the labeling head.
According to the invention, the gripper means is arranged on the labeling head in such a manner that when it holds a label, a corner of the label coincides substantially with the point of intersection of the pivot axis with the plane of the label.
Thus, in order to position the label correctly on an article, the conveyor is caused to advance and the labeling head is moved so that the pivot axis intersects both the corner of the label and the reference point on the article. The label then pivots with the labeling head so that its corner continues to coincide with the reference point on the article, regardless of the angle through which the labeling head is pivoted. There is no longer any offset induced by the pivoting of the labeling head.
Advantageously, the labeling head has a printer with active print means and with means for driving the label through the printer, the gripper means being situated immediately downstream from the active print means.
Placing the active print means on board the labeling head, avoids incessant go-and-return trips of the labeling head between external print means and a labeling position overlying the conveyor of the labeling machine.
Advantageously, the active print means are controlled by control means that are not secured to the labeling head. The portions of the printer that are not active from the point of view of printing are thus located on the labeling machine, thereby simplifying the design of the labeling head.
Preferably, the active print means are adapted to receive a strip supporting adhesive labels coming from a roll, the labeling head having deflector members for imparting a twisted trajectory to the strip between the roll and the active print means.
By xe2x80x9ctwistedxe2x80x9d, it should be understood that the midplane of the strip does not remain constant as the strip travels between the roll and the active print means. The roll is thus offset from the active print means, thus making it possible to design a labeling head that presents a smaller moment of inertia, and that is of more compact structure.
In a first embodiment, the roll is placed on the labeling head beside the active print means. The roll is thus placed close to the axis of rotation of the labeling head, thereby reducing its moment of inertia.
In a second embodiment, the roll is mounted to rotate on the structure of the labeling machine, with the deflector members comprising a deflector cylinder secured to the labeling head and extending parallel to the pivot axis of the labeling head. In this way, the labeling head is lightened by a weight corresponding to the weight of the roll, and because of the deflection parallel to its pivot axis, the labeling head can still be oriented at any angle while nevertheless ensuring that the support strip is fed properly.
Advantageously, separation means for separating the support strip from the label are located between the active print means and the gripper means, such separation means being associated with means for re-winding the support strip.
Preferably, the gripper means comprise a suction member holding the label via a non-adhesive face thereof.
The gripper means is then associated with placing means comprising a pusher movable in a direction parallel to the pivot axis of the labeling head and pushing the label by means of its non-adhesive face towards the article that is to be labeled.
In order to position the label relative to the article that is to be labeled, the structure includes a bracket forming a support for the labeling head, the labeling head being movable along the bracket in a direction perpendicular to its pivot axis and perpendicular to a travel direction of the article to be labeled.